pub fn new_birthday_probability(n: u32) -> f64 {
    if n >= 365 {
        return 1.0000;
    }
    let mut i = 0;
    let mut res = 1.0;
    while i < n {
        res *= (365.0 - i as f64) / 365.0;
        i += 1;
    }
    let res = format!("{:.4}", 1.0 - res).parse::<f64>().unwrap();
    res
}
